首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   210322篇
  免费   15273篇
  国内免费   754篇
耳鼻咽喉   2291篇
儿科学   5483篇
妇产科学   4304篇
基础医学   27102篇
口腔科学   4514篇
临床医学   20003篇
内科学   44927篇
皮肤病学   2756篇
神经病学   20307篇
特种医学   6959篇
外国民族医学   13篇
外科学   32956篇
综合类   3411篇
现状与发展   2篇
一般理论   291篇
预防医学   19065篇
眼科学   4373篇
药学   14388篇
  1篇
中国医学   376篇
肿瘤学   12827篇
  2023年   844篇
  2022年   1407篇
  2021年   3440篇
  2020年   2112篇
  2019年   3393篇
  2018年   3967篇
  2017年   3212篇
  2016年   3410篇
  2015年   4066篇
  2014年   6095篇
  2013年   8822篇
  2012年   13124篇
  2011年   14319篇
  2010年   8096篇
  2009年   7305篇
  2008年   13588篇
  2007年   14430篇
  2006年   13918篇
  2005年   14397篇
  2004年   13810篇
  2003年   12899篇
  2002年   12435篇
  2001年   1874篇
  2000年   1461篇
  1999年   2048篇
  1998年   2828篇
  1997年   2437篇
  1996年   2205篇
  1995年   1953篇
  1994年   1755篇
  1993年   1655篇
  1992年   1209篇
  1991年   1149篇
  1990年   1054篇
  1989年   954篇
  1988年   1013篇
  1987年   1018篇
  1986年   998篇
  1985年   1081篇
  1984年   1478篇
  1983年   1461篇
  1982年   1814篇
  1981年   1639篇
  1980年   1555篇
  1979年   812篇
  1978年   958篇
  1977年   932篇
  1976年   833篇
  1975年   683篇
  1974年   666篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz - Der Bezug staatlicher Transferleistungen (STL) in Deutschland ist mit dem Verzicht auf sichere Verhütung assoziiert. Die...  相似文献   
62.
Inhalation of ash can be of great concern for affected communities, during and after volcanic eruptions. Governmental and humanitarian agencies recommend and distribute a variety of respiratory protection (RP), most commonly surgical masks. However, there is currently no evidence on how effective such masks are in protecting wearers from volcanic ash. In Part I of this study (Mueller et al., 2018), we assessed the filtration efficiency (FE) of 17 materials from different forms of RP against volcanic ash and a surrogate, low-toxicity dust, Aloxite. Based on those results, we now present the findings from a volunteer simulation study to test the effect of facial fit through assessment of Total Inward Leakage (TIL).Four different disposable RP types that demonstrated very high median FE (≥96% for Aloxite; ≥89% for volcanic ash) were tested without provision of training on fit. These were an industry-certified mask (N95-equiv.); a surgical mask from Japan designed to filter PM2.5; a flat-fold basic mask from Indonesia; and a standard surgical mask from Mexico, which was also tested with an added medical bandage on top, as an additional intervention to improve fit.Ten volunteers (6 female, 4 male) were recruited. Each RP type was worn by volunteers under two different conditions simulating cleaning-up activities during/after volcanic ashfall. Each activity lasted 10?min and two repeats were completed for each RP type per activity. Dust (as PM2.5) concentration inside and outside the mask was measured with two TSI SidePak aerosol monitors (Models AM510 and AM520, TSI, Minnesota, USA) to calculate TIL. A questionnaire was administered after each test to collect perceptions of fit, comfort, protection and breathability.The best-performing RP type, across both activities, was the industry-certified N95-equiv. mask with 9% mean TIL. The standard surgical mask and the basic flat-fold mask both performed worst (35% TIL). With the additional bandage intervention, the surgical mask mean TIL improved to 24%. The PM2.5 surgical mask performed similarly, with 22% TIL. The N95-equiv. mask was perceived to provide the best protection, but was also perceived as being uncomfortable and more difficult to breathe through.This study provides a first objective evidence base for the effectiveness of a selection of RP types typically worn around the world during volcanic crises. The findings will help agencies to make informed decisions on the procurement and distribution of RP in future eruptions.  相似文献   
63.
64.
Personal care product use is a potential source of metals exposure among children, but studies have been limited. We measured urinary concentrations of 10 metals (aluminum, arsenic [As], barium [Ba], cadmium, cobalt [Co], lead [Pb], manganese [Mn], molybdenum [Mo], nickel, and zinc [Zn]) in third trimester pregnant women (n?=?212) and their children at 8–14 years of age (n?=?250). Demographic factors (child sex, age, socioeconomic status, and maternal education), body mass index (BMI) z-score, and child personal care product use in the 24?h prior to urine collection were examined as predictors of urinary metal concentrations. Metals were detected in 80–100% of urine samples, with significant differences in maternal versus childhood levels. However, metal concentrations were not strongly correlated within or between time points. In linear regression models including all demographic characteristics, BMI z-score, and specific gravity, age was associated with higher Co (6% [95% CI: 2, 10]), while BMI z-score was associated with lower Mo (-6% [95% CI: -11, -1). In addition, significantly higher metal concentrations were observed among users of colored cosmetics (Mo: 42% [95% CI: 1, 99]), deodorant (Ba: 28% [3, 58]), hair spray/hair gel (Mn: 22% [3, 45]), and other toiletries (As: 50% [9, 108]), as well as with an increasing number of personal care products used (As: 7% [3, 11]) after adjustment for child sex, age, total number of products used, and specific gravity. However, significantly lower metal concentrations were noted for users of hair cream (As and Zn: -20% [-36, -2] and -21% [-35, -2], respectively), shampoo (Pb: -40% [-62, -7]), and other hair products (Pb: -44% [-65, -9]). We found that personal care product use may be a predictor of exposure to multiple metals among children. Further research is recommended to inform product-specific exposure source identification and related child health risk assessment efforts.  相似文献   
65.

Background

The prevalence of knee osteoarthritis is increasing worldwide. Obesity is an important modifiable risk factor for both the incidence and progression of knee osteoarthritis. Consequently, international guidelines recommend all patients with knee osteoarthritis who are overweight receive support to lose weight. However, few overweight patients with this condition receive care to support weight loss. Telephone-based interventions are one potential solution to provide scalable care to the many patients with knee osteoarthritis. The objective of this study is to evaluate, from a societal perspective, the cost-utility and cost-effectiveness of a telephone-based weight management and healthy lifestyle service for patients with knee osteoarthritis, who are overweight or obese.

Methods

An economic evaluation was undertaken alongside a pragmatic randomised controlled trial. Between May 19 and June 30, 2015, 120 patients with knee osteoarthritis were randomly assigned to an intervention or usual care control group in a 1:1 ratio. Participants in the intervention group received a referral to an existing non-disease specific 6-month telephone-based weight management and healthy lifestyle service. Quality-adjusted life years (QALYs) was the utility measure and knee pain intensity, disability, weight, and body mass index (BMI) were the clinical measures of effect. Costs included intervention costs, healthcare utilisation costs (healthcare services and medication use) and absenteeism costs due to knee pain. Data was collected at baseline, 6?weeks and 26?weeks. The primary cost-effectiveness analysis was performed from the societal perspective.

Results

Mean cost differences between groups (intervention minus control) were $493 (95%CI: -3513 to 5363) for healthcare costs, $-32 (95%CI: -73 to 13) for medication costs, and $125 (95%CI: -151 to 486) for absenteeism costs. The total mean difference in societal costs was $1197 (95%CI: -2887 to 6106). For QALYs and all clinical measures of effect, the probability of the intervention being cost-effective compared with usual care was less than 0.36 at all willingness-to-pay values.

Conclusions

From a societal perspective, telephone-based weight loss support, provided using an existing non-disease specific 6-month weight management and healthy lifestyle service was not cost-effective in comparison with usual care for overweight and obese patients with knee osteoarthritis.

Trial registration number

ACTRN12615000490572, registered 18th May 2015
  相似文献   
66.
Understanding of indoor air quality (IAQ) during and after spray polyurethane foam (SPF) application is essential to protect the health of both workers and building occupants. Previous efforts such as field monitoring, micro-chamber/spray booth emission studies, and fate/transport modeling have been conducted to understand the chemical exposure of SPF and guide risk mitigation strategies. However, each type of research has its limitation and can only reveal partial information on the relationship between SPF and IAQ. A comprehensive study is truly needed to integrate the experimental design and analytical testing methods in the field/chamber studies with the mathematical tools employed in the modeling studies. This study aims to bridge this gap and provide a more comprehensive understanding on the impact of SPF to IAQ. The field sampling plan of this research aims to evaluate the airborne concentrations of methylene diphenyl diisocyanate (MDI), formaldehyde, acetaldehyde, propionaldehyde, tris(1-chlor-2-propyl)phosphate (TCPP), trans-1-chloro-3,3,3-trifluoropropene (SolsticeTM), and airborne particles. Modifications to existing MDI sampling and analytical methods were made so that level of quantification was improved. In addition, key fate and transport modeling input parameters such as air changes per hour and airborne particle size distribution were measured. More importantly, TCPP accumulation onto materials was evaluated, which is important to study the fate and transport of semi-volatile organic compounds. The IAQ results showed that after spray application was completed in the entire building, airborne concentrations decreased for all chemicals monitored. However, it is our recommendation that during SPF application, no one should return to the application site without proper personal protection equipment as long as there are active spray activities in the building. The comparison between this field study and a recent chamber study proved surface sorption and particle deposition is an important factor in determining the fate of airborne TCPP. The study also suggests the need for further evaluation by employing mathematical models, proving the data generated in this work as informative to industry and the broader scientific community.  相似文献   
67.
68.
69.
The appropriateness of dental manpower has become a great uncertainty in the changing practice of dentistry. This paper presents research on the requirement for and supply of dental services in Victoria between 1984 and 1996. The requirement for dental services was found to be increasing due to population growth and higher per capita demand due to decreased endentulism. The supply of dental services was found to be mildly decreasing due to balanced supplementation and attrition processes and subtle sex ratio and age distribution changes among dentists. The resulting market excess, even after consideration of idle capacity and transfer of services supplied to dental therapists, provides a marked contrast to many, but not all, developed countries. It also offers an opportunity to shape occupational and specialty distribution to the advantage of dental professions and the public.  相似文献   
70.
Resection is the preferred treatment for oral squamous cell carcinoma, and pathological staging of the resected specimen is crucial. The role of molecular biology in the diagnosis of minimal residual disease has not been fully investigated and may improve staging. Multiple adjacent specimens were taken from the tumour, the invasive front, the surgical margin, and the lymph nodes of 20 specimens from patients with oral cancer. Bisulphite-treated DNA from these specimens was assayed quantitatively with pyrosequencing methylation assays (PMA) of CpG islands within the gene promoters of the p16 and CYGB genes. Results were recorded with histopathological results, and compared with clinical outcome. Biological and technical replicates confirmed the reliability of the techniques. PMA upgraded 13 of the 20 surgical margins, 6 of which subsequently had a recurrent tumour. Not all of these recurrences were predicted and the effects of adjuvant treatment make firm conclusions difficult.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号